By pleading guilty, Dunn admitted that in April 2011 he wrote: “I hate you and will do anything I can to get rid of you. You will die at my hands. I will kill you Barack Obama.”

A sentencing date will not be set until U.S. Probation and Pre-Trial Services conduct a presentence report.

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U.S. District Judge John Woodcock, who accepted Dunn’s plea and will impose a sentence, said Wednesday that it would be helpful to him if Dunn were to be evaluated by a psychiatrist and physician employed by the U.S. Bureau of Prisons.

The defendant suffers from Marfan syndrome, defense attorney Stephen Smith of Bangor told the judge Wednesday. Marfan syndrome is a disorder of the body’s connective tissues that can result in disproportionately long arms and legs, among other symptoms.

Dunn’s mother, Philomena Gordon of Bingham, has said her son is mentally disabled. She also has noted that he suffers from the effects of Marfan syndrome.

Gordon said her son stands 7 feet, 6 inches tall and weighs more than 300 pounds. She told the Lewiston Sun Journal earlier this year that Dunn should be under supervised medical and psychiatric care, not behind bars.

He has been incarcerated at the Maine Correctional Center in Windham for about 1½ years on the drug charge, Smith told the judge Wednesday. Dunn most likely would not begin serving his federal sentence until he has served the state sentence.

Dunn isn’t the first inmate to be charged with threatening a president. Charles D. Miles, 32, of Skowhegan was sentenced in January 2007 to eight years in prison for threatening to kill two presidents, a governor, a federal judge and other public officials in letters penned over a four-year period.

Miles, who is due to be released from federal prison in November 2012, was committed to the former Augusta Mental Health Institute in 2000 after he was found not criminally responsible for setting the March 1999 fire that leveled the historic grandstand exhibition hall in Skowhegan. The fire caused $3 million in damage.

He is expected to be returned to Riverview Psychiatric Center, formerly AMHI, when he is released this fall.